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Old 10-10-2012, 06:50   #1
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Holding Tank Configuaration Option

Here's an option for installing a holding tank without a Y-valve and yet fully in compliance with US regulations. I like this configuration for it's simplicity.



This diagram is simplistic in that, for clarity, it doesn't show the actual vertical heights of all the hose conections. The effluent from the holding tank is best exiting the tank near the top though the pick up tube draws from the bottom of the tank. At this holding tank exit a T-fitting offers a pathway up a rising hose to the deck pump out and the other T pathway to a descending hose to a macerator pump. It's important that the rising and falling spans do not trap contents in dips of the hose run. Although there is a vented loop in my diagram, I elected not to keep this in my system. No Y-valve is required as the closed deck pump out cover allows for the macerator to maintain suction from the pump and while the macerator is not on the deck pump out draws easily from the tank. Unlike the diagram I have two vents at the top of my holding tank to promote more oxygen flow and aerobic bacteria,- anaerobes stink! Complance with regulation is achieved, for me, by locking the cabinet that contains the through hull valve and having the handle removed from the valve while it is in the closed position.
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Old 10-10-2012, 06:57   #2
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Re: Holding Tank Configuaration Option

Much like our OEM system; no Y-valve, but a ball valve on the thru-hull...

BTW, you must have come back through this area when I wasn't paying attention

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Old 10-10-2012, 07:00   #3
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Re: Holding Tank Configuaration Option

CaptForce, We are preparing to install a holding tank in our sailboat down in the BVI's and have been advised that a system very similar to your drawing is what all of the charter operators are going with from the factory due to its simplicity and reliability. We have been advised to mount the holding tank as high as is practical so the the gravity flow to the 2" thru-hull will readily flush the tank when offshore.
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Old 10-10-2012, 07:14   #4
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Re: Holding Tank Configuaration Option

Mine's that way , except for a Y valve at the intersection of the two discharge paths. W/O a way to close off one when pumping/sucking via the other how do you draw the required vacuum?

Never mind I see the difference!
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Old 10-10-2012, 07:51   #5
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Re: Holding Tank Configuaration Option

One of my boats has that minus the macerator - simpler still. Just open the through hull and the tank drains. I prefer boats that put the through-hull under the head vanity - just open the cabinet door and there it is. Very accessible, but out of sight.
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Old 10-10-2012, 08:01   #6
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Re: Holding Tank Configuaration Option

Why? Why do folks continue to suggest putting everything through their holding tank whether it goes overboard or not?
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Old 10-10-2012, 08:36   #7
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Re: Holding Tank Configuaration Option

That's the way my boat is set up. I think it was Peg Hall who suggested installing a key switch to control the macerator pump. That way you don't need to lock the seacock. I think that would simplify the system even more.

The reason I used this system is that the vast majority of my boating is done in waters were direct discharge is not allowed. If I did long offshore passages, I might install a Y valve to allow direct discharge.
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Old 10-10-2012, 08:38   #8
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Re: Holding Tank Configuaration Option

This looks like a simple system, but one caveat: how do you change out the macerator should it fail? I'd consider a second valve between the holding tank and the macerator pump. This was the scenario that happened to us this summer, although we have the conventional Y-valve plumbing arrangement. The macerator pump failed, and therefor was letting air in, therefore we couldn't get the vacuum to pump out the holding tank - in your setup as diagrammed, without the valve to isolate the macerator pump, replacing it would be an unbearable proposition as you would be doused with the contents of the holding tank.
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Old 10-10-2012, 09:09   #9
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Re: Holding Tank Configuaration Option

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Originally Posted by Stu Jackson View Post
Why? Why do folks continue to suggest putting everything through their holding tank whether it goes overboard or not?
In a simple gravity feed system, the holding tank basically increases the volume of the discharge line, allowing one to hold waste, with no secondary holding system needed. It allows waste to be held when in an anchorage where it's inappopriate to dump, but easily be dumped once it's appropriate to do so. If it's approprate to dump when used, simply leave the through hull open and it functions as a stright discharge. Placed correctly, and the tank itself will automatically get flushed at the bottom by sea water.

Given that one simple system requires no pumping, no y-valve, and only one through hull, my question is: why create a second holding system that adds complexity and requires a pump out station (or second discharge system) to empty the holding tank?
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Old 10-10-2012, 12:09   #10
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Re: Holding Tank Configuaration Option

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Originally Posted by nautical62 View Post
One of my boats has that minus the macerator - simpler still. Just open the through hull and the tank drains. I prefer boats that put the through-hull under the head vanity - just open the cabinet door and there it is. Very accessible, but out of sight.

Our holding tank wouldn't drain, it would fill. Ours needs the macerator to empty, and then the ball valve must be closed right away...

-Chris
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Old 10-10-2012, 12:20   #11
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Re: Holding Tank Configuaration Option

Mine is simpler, still! The holding tank is located above the waterline. It has twin 1 1/2" vent hoses to either side of the bow, allowing use of aerobic bacteria from Peggy Halls' K.O.. The waste goes into the holding tank, and if the water level valve is open, directly over the side.
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Old 10-10-2012, 13:06   #12
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Re: Holding Tank Configuaration Option

Mine is like the OP but instead of a macerator I have a manual diaphragm pump. All my openings are on top of the tank. The outflow has a pickup tube, so except for a low spot waste doesn't fill or remain in the hose. The pump is up high as well. (Except when pumping of course.)

The pump has a removable handle, so I'm calling that my lock out from pumping overboard.

John
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Old 11-10-2012, 15:17   #13
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Re: Holding Tank Configuaration Option

dumb question... and I know I should know better, but I just can't get my brain wrapped around this one:

When the macerator isn't running, it acts as a valve in the 'off' position? So there is no chance of backflow from, say, the ocean to the holding tank?
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Old 11-10-2012, 15:26   #14
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Re: Holding Tank Configuaration Option

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dumb question... and I know I should know better, but I just can't get my brain wrapped around this one:

When the macerator isn't running, it acts as a valve in the 'off' position? So there is no chance of backflow from, say, the ocean to the holding tank?

Our macerator is NOT a positive valve stop... but the ball-valve at the thru hull is. So in ours, open the ball valve on the (underwater) thru-hull, activate the macerator, holding tank empties, macerator off, ball valve closed, done.

With the thru hull ball valve open and macerator off, sea water invades the holding tank to the point of equilibrium... which is pretty much "full."

(Perhaps I should clarify: Our head is electric, so has it's own macerator pump that moves effluent from bowl to holding tank. That's NOT the same macerator pump (above) that empties the holding tank.)

-Chris
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Old 11-10-2012, 15:35   #15
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Re: Holding Tank Configuaration Option

Macerator pumps which use rubber impellers after the chopper blades should act as a closed valve. If the impeller or housing is worn I imagine there could be leakage. My tank is partially below the waterline and my pump (Jabsco) is below the waterline. Nothing flows back to the tank when the seacock is open.
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